#!/bin/sh
# ============================================
# celeryd - Starts the Celery worker daemon.
# ============================================
#
# :Usage: /etc/init.d/celeryd {start|stop|restart|status}
# :Configuration file: /etc/sysconfig/celeryd
#
# See http://docs.celeryproject.org/en/latest/tutorials/daemonizing.html

### BEGIN INIT INFO
# Provides:          celeryd
# Required-Start:    $network $local_fs $remote_fs
# Required-Stop:     $network $local_fs $remote_fs
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: celery task worker daemon
### END INIT INFO

# Source the centos service helper functions
source /etc/init.d/functions
# NOTE: "set -e" does not work with the above functions,
# which use non-zero return codes as non-error return conditions

# some commands work asyncronously, so we'll wait this many seconds
SLEEP_SECONDS=5

DEFAULT_PID_FILE="/var/run/celery/%n.pid"
DEFAULT_LOG_FILE="/var/log/celery/%n.log"
DEFAULT_LOG_LEVEL="INFO"
DEFAULT_NODES="celery"
DEFAULT_CELERYD="-m celery.bin.celeryd_detach"

#"如果$CELERY_DEFAULTS存在且不为空，CELERY_DEFAULTS就是$CELERY_DEFAULTS"  
#"如果$CELERY_DEFAULTS不存在或为空，那么CELERY_DEFAULTS就是/etc/celeryd.conf"
CELERY_DEFAULTS=${CELERY_DEFAULTS:-"/etc/celeryd.conf"}

#test –f File 文件存在并且是正规文件
#. file 等价于 source file
test -f "$CELERY_DEFAULTS" && . "$CELERY_DEFAULTS"

# Set CELERY_CREATE_DIRS to always create log/pid dirs.
#"如果$CELERY_CREATE_DIRS存在且不为空，CELERY_CREATE_DIRS就是$CELERY_CREATE_DIRS"  
#"如果$CELERY_CREATE_DIRS不存在或为空，那么CELERY_CREATE_DIRS就是0"
CELERY_CREATE_DIRS=${CELERY_CREATE_DIRS:-0}
CELERY_CREATE_RUNDIR=$CELERY_CREATE_DIRS
CELERY_CREATE_LOGDIR=$CELERY_CREATE_DIRS

#"如果$CELERYD_PID_FILE 为空"
if [ -z "$CELERYD_PID_FILE" ]; then
    CELERYD_PID_FILE="$DEFAULT_PID_FILE"
    CELERY_CREATE_RUNDIR=1
fi

#"如果$CELERYD_LOG_FILE 为空"
if [ -z "$CELERYD_LOG_FILE" ]; then
    CELERYD_LOG_FILE="$DEFAULT_LOG_FILE"
    CELERY_CREATE_LOGDIR=1
fi

CELERYD_LOG_LEVEL=${CELERYD_LOG_LEVEL:-${CELERYD_LOGLEVEL:-$DEFAULT_LOG_LEVEL}}
CELERYD_MULTI=${CELERYD_MULTI:-"celeryd-multi"}
CELERYD=${CELERYD:-$DEFAULT_CELERYD}
CELERYD_NODES=${CELERYD_NODES:-$DEFAULT_NODES}

# This is used to change how Celery loads in the configs.  It does not need to
# be set to be run.
export CELERY_LOADER

#"-n:如果$2 非空(非0），返回0(true)"  
if [ -n "$2" ]; then
    CELERYD_OPTS="$CELERYD_OPTS $2"
fi

#"dirname:截取给定路径的目录部分"
CELERYD_LOG_DIR=`dirname $CELERYD_LOG_FILE`
CELERYD_PID_DIR=`dirname $CELERYD_PID_FILE`

# Extra start-stop-daemon options, like user/group.
if [ -n "$CELERYD_USER" ]; then
    DAEMON_OPTS="$DAEMON_OPTS --uid=$CELERYD_USER"
fi
if [ -n "$CELERYD_GROUP" ]; then
    DAEMON_OPTS="$DAEMON_OPTS --gid=$CELERYD_GROUP"
fi

if [ -n "$CELERYD_CHDIR" ]; then
    DAEMON_OPTS="$DAEMON_OPTS --workdir=\"$CELERYD_CHDIR\""
fi

check_dev_null() {
	#"-c:FILE存在，是特殊字符"
    if [ ! -c /dev/null ]; then
        echo "/dev/null is not a character device!"
        exit 75  # EX_TEMPFAIL
    fi
}


maybe_die() {
	#"-ne:不等于"
    if [ $? -ne 0 ]; then
        echo "Exiting: $* (errno $?)"
        exit 77  # EX_NOPERM
    fi
}

create_default_dir() {
    if [ ! -d "$1" ]; then
        echo "- Creating default directory: '$1'"
        mkdir -p "$1"
        maybe_die "Couldn't create directory $1"
        echo "- Changing permissions of '$1' to 02755"
        chmod 02755 "$1"
        maybe_die "Couldn't change permissions for $1"
        if [ -n "$CELERYD_USER" ]; then
            echo "- Changing owner of '$1' to '$CELERYD_USER'"
            chown "$CELERYD_USER" "$1"
            maybe_die "Couldn't change owner of $1"
        fi
        if [ -n "$CELERYD_GROUP" ]; then
            echo "- Changing group of '$1' to '$CELERYD_GROUP'"
            chgrp "$CELERYD_GROUP" "$1"
            maybe_die "Couldn't change group of $1"
        fi
    fi
}


check_paths() {
    if [ $CELERY_CREATE_LOGDIR -eq 1 ]; then
        create_default_dir "$CELERYD_LOG_DIR"
    fi
    if [ $CELERY_CREATE_RUNDIR -eq 1 ]; then
        create_default_dir "$CELERYD_PID_DIR"
    fi
}

create_paths() {
    create_default_dir "$CELERYD_LOG_DIR"
    create_default_dir "$CELERYD_PID_DIR"
}

export PATH="${PATH:+$PATH:}/usr/sbin:/sbin"


_get_pid_files() {
    [[ ! -d "$CELERYD_PID_DIR" ]] && return
    echo $(ls -1 "$CELERYD_PID_DIR"/*.pid 2> /dev/null)
}

stop() {
    local pid_files=$(_get_pid_files)
    [[ -z "$pid_files" ]] && echo "celeryd is stopped" && return 0

    local one_failed=
    for pid_file in $pid_files; do
        local pid=$(cat "$pid_file")
        echo -n $"Stopping celeryd (pid $pid): "

        # killproc comes from 'functions' and brings three nice features:
        #  1. sending TERM, sleeping, then sleeping more if needed, then sending KILL
        #  2. handling 'success' and 'failure' output
        #  3. removes stale pid files, if any remain
        killproc -p "$pid_file" -d "$SLEEP_SECONDS" celeryd || one_failed=true
        echo
    done

    [[ "$one_failed" ]] && return 1 || return 0
}

start() {
    echo -n $"Starting celeryd: "

    # If Celery is already running, bail out
    local pid_files=$(_get_pid_files)
    if [[ "$pid_files" ]]; then
        echo -n $"celeryd is already running. Use 'restart'."
        failure
        echo
        return 1
    fi

    $CELERYD_MULTI start $CELERYD_NODES $DAEMON_OPTS        \
                         --pidfile="$CELERYD_PID_FILE"      \
                         --logfile="$CELERYD_LOG_FILE"      \
                         --loglevel="$CELERYD_LOG_LEVEL"    \
                         --cmd="$CELERYD"                   \
                         --quiet                            \
                         $CELERYD_OPTS

    if [[ "$?" == "0" ]]; then
        # Sleep a few seconds to give Celery a chance to initialize itself.
        # This is useful to prevent scripts following this one from trying to
        # use Celery (or its pid files) too early.
        sleep $SLEEP_SECONDS
        pid_files=$(_get_pid_files)
        if [[ "$pid_files" ]]; then
            for pid_file in $pid_files; do
                local node=$(basename "$pid_file" .pid)
                local pid=$(cat "$pid_file")
                echo
                echo -n "    $node (pid $pid):"
                success
            done
            echo
            return 0
        else  # celeryd_multi succeeded but no pid files found
            failure
        fi
    else  # celeryd_multi did not succeed
        failure
    fi
    echo
    return 1
}

check_status() {
    local pid_files=$(_get_pid_files)
    [[ -z "$pid_files" ]] && echo "celeryd is stopped" && return 1
    for pid_file in $pid_files; do
        local node=$(basename "$pid_file" .pid)
        status -p "$pid_file" $"celeryd (node $node)" || return 1  # if one node is down celeryd is down
    done
    return 0
}

case "$1" in
    start)
        check_dev_null
        check_paths
        start
    ;;

    stop)
        check_dev_null
        check_paths
        stop
    ;;

    status)
        check_status
    ;;

    restart)
        check_dev_null
        check_paths
        stop && start
    ;;

    *)
        echo "Usage: /etc/init.d/celeryd {start|stop|restart|status}"
        exit 3
    ;;
esac

exit $?
